Convert XLR to TRS Headphone Cable Issue

The headphone amp is model MX-HPA...it was sold as new and heavily discounted.  Remember, I am not well educated on electrical matters...but have learned (I think) a lot in the past few days.  This amp is advertised as "Fully Balanced" with a pair of combo TRS/3-pin XLT output connectors...while the output connector to the headphone allows TRS or 3-pin XLR connectors, not a 4 pin outlet which balanced to balanced-designed headphone would seem to require....and my experience with a 3-pin XLR to TRS adapter cable (proper continuity confirmed) is that the XLR termination does not convey sound staging 9sounds mono), but with the TRS termination using the headphone cable without the adapter, I get full sound staging and musicality.  I'm beginning to think that there is an issue with the AMP. I should get proper sound staging with the 3-pin XLR connector irrespective of whether it was balanced or not...presumably the manufacturer has that figured out and properly wired everything...or not.  Its at the selling dealer today to be analyzed...will be interested to see if they can replicate my experience. So far, they have been excellent to deal with, but I doubt it can be "fixed" for XLR functionality, and a replacement is likely to have the same issues.  But I'm happy with TRS-only connection based upon what I heard before I got the 3-pin XLR to TRS adapter cable.  

When you are talking about balanced headphones and headphone amps, it's a marketing gimmick. There is no such thing. The people that make this stuff use the term balanced, put xlr connectors on the gear and hope you don't ask too many questions. Here's what's really going on. Any time you see the work balanced, insert the word bridged. A balanced headphone amp is really a bridged amp. Bridging combines 2 channels into one, so your headphone amp has 4 channels. Single ended stereo signal transfer requires 3 conductors. Left and right channels and a common ground. You have 4 power amps and 3 wires. The incoming signal is converted to balanced inside the headphone amp. After the conversion, you now have 2 signals and 2 separate grounds and can make use of all 4 channels. The "balanced" output for your headphones usually requires a TRRS connector, or something else that supports 4 conductors. If your headphones have a hardwired connection, you can't use them on the output that's labeled balanced, and you can't bridge the amp. Most people think that the TRRS headphone jack labeled balanced, is balanced. Its not. That's why there is no such thing. Headphones are just a really small pair of speakers. If you want to call headphones balanced, you have to call the speakers in your living room balanced as well. You can only use your headphones if you have a detachable cable. Now that the ground is separated from the bridging process, each speaker in the headphone gets its own ground, just like any other pair of speakers. They get to use the term balanced because the signal had to be split at the input to separate the common ground. So, if you want your headphones to work properly, you can't bridge the amp. 

The reason they try to hide this from you is there are some downsides to bridging amps. A bridged 2 channel amp sees half the resistance of a mono amp. For example, if you have an 8 ohm speaker, it becomes a 4 ohm load when you connect it to a bridged amp. You're forcing the amp to work twice as hard to drive the same load in unbridged mode. If you look at the specs on your headphone amp, you see the amp makes 2x the power in "balanced" mode. If your headphones are hard to drive, they may sound better with the amp bridged. If not, unbridged usually sounds better. If you want to use your amp in bridged mode, you'll need to get headphones that have a detachable cable, and a TRRS cable.  

Well, while I appreciate everyone's thoughts and comments, the discussion of balanced vs. single ended is probably moot at this point...the question now is why will the amp not convey proper signal to a 3-pin XLR connector while sending a proper signal to the TRS connector?  "Proper" = fully musical and noticeable sound staging.  My suspicion is manufacturer's or component's error as the outlet connector is a "'combo" configuration, accepting either a TRS or 3-pin XLR termination from the headphone cable...either should function the same if properly installed and functional.  Its at the dealer now being evaluated...will see what they discover.

052rc

When you are talking about balanced headphones and headphone amps, it’s a marketing gimmick. There is no such thing.

Sorry, but you really don’t know what you’re talking about.

Here’s what’s really going on. Any time you see the work balanced, insert the word bridged. A balanced headphone amp is really a bridged amp.

No, they’re two different things. For example, a balanced differential amplifier. Or a balanced component that uses transformers at its inputs and output. Please get your facts straight.

Now that the ground is separated from the bridging process, each speaker in the headphone gets its own ground, just like any other pair of speakers.

Actually, what’s most common is that balanced headphone amplifiers use no ground to the headphone. That’s why there are only four conductors: a positive and negative phase for each channel. Note that the negative phase is just that - it’s not tied straight to ground.

I think the confusion may be that the line level inputs to the MX-HPA will accept both single ended connection via RCA jacks or balanced connection via the XLR jacks, on the rear of the unit. The headphone outputs on the front of the unit are not balanced. Balanced connections are only required for microphone or line-level signals that will be further amplified and any noise induced by a long cable needs to be eliminated. Headphones are basically mini speakers with a hot and neutral input to left and right just like a normal speaker. The typical TRS plug of most headphone cables uses the tip for the left hot signal, the ring for the right hot and the sleeve to provide neutral to both sides. The XLR portion of the combo jacks for the headphone out are probably wired for pin 2 left hot, pin 3 for right hot and pin 1 for neutral for both sides. The OP's complaint may stem from the XLR to TRS extension cable being mis-wired so that L and R are either being summed to mono or only the L or R are being fed to each ear cup, resulting in mono presentation.